Radio receivers are increasingly being controlled by microcomputers, with evaluation of a signal representing the signal level also being performed. Such a signal is derived, for example, by amplitude demodulation followed by low-pass filtration of the FM intermediate frequency signal. Following further processing by the microcomputer, a signal strength signal of this kind is used to reduce stereo channel separation or volume when noise occurs and to select one of several transmitters broadcasting the same program. Processing the signal strength signal in the microcomputer, especially determining the change direction, entails computing cost.
The goal of the present invention is to derive a signal as a function of the change direction of the incoming signal level, using minimum computing power.